After Hurricane Florence deposited its last drop of rain on the Carolinas, the worst of the flooding was still to come as water made its way down mountainsides, through gullies and into creeks and accumulated in the Cape Fear River.

Spilling over the river’s banks, the water reached and breached a cooling lake used by Charlotte-based Duke Energy’s L.V. Sutton power plant in Wilmington, North Carolina. From there it flowed over one of the three surrounding coal ash disposal sites, prompting fears that the cancer-causing byproduct of bygone coal operations could be flowing through a major groundwater system.

Tests upstream and downstream from the facility ultimately showed that little-to-no leaking occurred at the site, according to the company. The state’s environmental agency and outside environmental groups have collected their own samples, with results still pending.

The state’s environmental agency confirmed those results in a test released on Oct. 4, although environmentalists from the Waterkeeper Alliance alleged their own results showed increased signs of arsenic as a result of the flooding.

The toxic ash was left by a coal-burning plant the company retired in 2013 and replaced with one fueled by natural gas — an increasingly common occurrence as utilities move away from coal in favor of the cheaper fuel.

Still, the coal plant’s legacy hangs over the site, and the problems from the hurricane may provide a lesson for any community where coal-burning plants are being retired.

Some 217 coal plants have been retired or marked for retirement since 2010, according to the Sierra Club’s Beyond Coal Campaign, which launched in the same year.

“Coal plants tend to be located on bodies of water,” said Mary Anne Hitt, director of the campaign, which aims to close coal plants through legal intervention because of their climate-warming carbon emissions. “And that has now created this legacy of water pollution in hundreds of communities across the country and they are waking up to the realization that their drinking water is filled with cancer-causing chemicals.”

Coal plants can spit out a variety of byproducts harmful to public health. Chief among those is in the coal ash, also known as coal combustion residuals, which contains pollutants like mercury, cadmium and arsenic that can leach into nearby waterways.

Approximately 130 million tons of coal ash were generated in 2014 alone, according to a report from the American Coal Ash Association.

Operators tend to take that coal ash and dispose of it in specialized landfills near their sites. The regulation of the waste has largely been left to the states, but after a series of high-profile spills in recent years, including some in North Carolina, the federal government, under the Obama administration, authored regulations directing stricter standards and monitoring for coal ash, including requirements to clean up unlined coal ash pits near waterways.

The Trump administration has already worked to roll back most of those regulations. The argument, according to the EPA, is that states are better equipped for such oversight.

“Our actions mark a significant departure from the one-size-fits-all policies of the past and save tens of millions of dollars in regulatory costs,” Acting EPA Administrator Andrew Wheeler said in a July 18 news release when the administration finalized new rules.

But environmental groups complained the action would diminish clean water protections.

“Once again the job is being kicked to the states, who have a poor track record, unfortunately, of actually taking care of this problem,” Hitt said. “Weakening our clean air and clean water standards is definitely not a good thing to be doing at a time where we are looking to decommission dozens of coal plants.”

While some plants are being converted to natural gas, most are simply being shut down — for good. In those cases, it’s often up to the operators to decide if they will demolish the buildings and clean up the site.

But unlike nuclear power plants slated for closure, there are no national standards for the decommissioning process at coal plants. Operators are largely free to determine how quickly, if ever, a plant will be torn down. In regulated electric markets like those covering the Southeast, operators must collect a fee from ratepayers to amass a fund to pay for the eventual shutdown and cleanup of plants.

There are no such requirements in deregulated markets, where the pace of coal plant retirements is faster. Larger energy companies may have such funds and disclose to shareholders how they’re to be used. Smaller generating companies and entities may lack resources for cleanups.

An October 2017 study on decommissioning by Resources for the Future, a nonpartisan, Washington-based research firm, could not find any evidence of funds set aside for decommissioning fossil or renewable plants operated by municipal or other smaller entities in Texas, which operates its own electricity markets.

According to data from 22 states assembled for the report, of 238 retired fossil fuel generating units, 38 percent have only been mothballed. The report, which admits its numbers are not comprehensive, identifies New Jersey as having the most shuttered plants with 37; Ohio has 13, Pennsylvania 11, Indiana seven and Illinois six.

Most of those plants have been retired since 2014, the report said, but nine units “have sat cold and dark for more than 10 years, raising concerns over blight and potentially loss of structural integrity,” the report said.

Utilities have the option to alter the plant to another generation source, or they could leave it sitting as a tax write-off. But the role of communities in that decision is usually determined on a case-by-case basis, according to Bill Schleizer, CEO of Delta Institute, a nonprofit working to inform communities of redevelopment opportunities for decommissioned coal plants.

“We have seen a spectrum: of really great engagement with the communities before closures are announced so that redevelopment plans are done in lockstep with community partners, to things not being told and being completely silent about it and then a plant being mothballed and held,” Schleizer said. “Because it’s done on a state-by-state and locality basis, there is no one thing we have seen. It’s really a spectrum of how plants work with their communities.”

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